Multi-stream image decoding apparatus and method

ABSTRACT

A capsule camera includes a wireless transmitter that transmits data and a receiving system having multiple receiving units to allowing storing multiple data streams simultaneously. The multiple stored data streams may be used at a later time to derive the best data stream for analysis, based on the network conditions at the time each data packet is received. The best data stream may be derived from the multiple stored data streams at a later time during the decoding process. For example, in a capsule camera application, the multiple data streams may be stored in the memory devices associated with the receiving units, which are typically attached to different locations on the body during diagnosis. The multiple data streams are maintained as the capsule passes through the gastrointestinal tract. Subsequently, after the diagnosis, the receiving units are recovered and connected to a computer or another standalone device for analysis. At that time, the best data stream is derived from the stored data streams using a decoding process, or by comparing the decoded results. Not all receiving units store the data streams at the same time. A screening process, for example, may be provided such that only the receiving units with better network conditions store the data streams. In a real-time system, the data streams may be stored for only a short duration before the best data stream is derived by a decoding process, or by comparing the decoded results.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a swallowable capsule camera forimaging of the gastro-intestinal (GI) tract. In particular, the presentinvention relates to a capsule camera that provides multiple video datastream to multiple receiving units for storage, from which a data streammay be derived for decoding and analysis.

2. Discussion of the Related Art

Devices for imaging body cavities or passages in vivo are known in theart and include endoscopes and autonomous encapsulated cameras.Endoscopes are flexible or rigid tubes that are passed into the bodythrough a body orifice or through a surgical opening, typically into theesophagus via the mouth or into the colon via the rectum. An image istaken at the distal end using a lens and the image data is transmittedto the proximal end outside the body, either by a lens-relay system orby a coherent fiber-optic bundle. A conceptually similar instrument mayrecord an image electronically at the distal end, for example using aCCD or CMOS array, and the image data is then transferred by electricalsignal to the proximal end over a cable. The endoscope is an instrumentthat allows a physician control over its field of view and is awell-accepted diagnostic tool. However, endoscopes have a number oflimitations, present risks to the patient, are invasive and areuncomfortable for the patient. The cost of these procedures restrictstheir application as routine health-screening tools.

Because of the difficulty in traversing a convoluted passage, endoscopescannot reach most of the small intestine and special techniques andprecautions, that add cost, are required to reach the entirety of thecolon. Endoscopic risks include the possible perforation of the bodilyorgans traversed and complications arising from anesthesia. Moreover, atrade-off must be made between patient pain during the procedure and thehealth risks and post-procedural down time associated with anesthesia.Endoscopies are necessarily in-patient services that involve asignificant amount of time from clinicians and thus are costly.

An alternative in vivo image sensor that addresses many of theseproblems is capsule endoscopy. In capsule endoscopy, a digital camera ishoused in a swallowable capsule, along with a radio transmitter fortransmitting image captured by the digital camera. The transmitted imagedata is received into a base-station receiver or transceiver forrecordation in a data recorder outside the body. The capsule camera mayalso include a radio receiver for receiving instructions or other datafrom a base-station transmitter. Instead of radio-frequencytransmission, lower-frequency electromagnetic signals may be used also.Power to the capsule may be supplied inductively from an external sourceor by a battery within the capsule.

An early example of a camera in a swallowable capsule is described inU.S. Pat. No. 5,604,531, issued to the Ministry of Defense, State ofIsrael. A number of patents assigned to Given Imaging (e.g., U.S. Pat.Nos. 6,709,387 and 6,428,469) describe such a system in greater detail.In each of these systems, the capsule camera includes a transmitter forsending the images captured to an external receiver. Other patentsissued to Olympus Corporation describe a similar technology. Forexample, U.S. Pat. No. 4,278,077 discloses a capsule camera for thestomach, which includes film in the camera. U.S. Pat. No. 6,939,292discloses a capsule with a memory and a transmitter.

An autonomous encapsulated camera with an internal battery has theadvantage that the measurements may be made with the patient ambulatory,out of the hospital, and with only moderate restrictions of activity.The base station includes an antenna array that is placed surroundingthe bodily region or regions of interest and this antenna array can betemporarily affixed to the skin or can be incorporated into a wearablevest. A data recorder is attached to a belt and includes a battery powersupply and data storage medium for saving the images received by theantenna array and any other data transmitted. The stored data issubsequently uploaded onto a diagnostic computer system for analysis.

A typical procedure using such a capsule camera consists of anin-patient visit in the morning during which a clinician attaches thebase station apparatus to the patient and the patient swallows thecapsule. The system begins recording images just prior to swallowing andcontinues to record images of the GI tract until the battery completelydischarges. Peristalsis propels the capsule through the GI tract. Therate of capsule passage through the GI tract depends on the degree ofmotility. Usually, the small intestine is traversed in 4 to 8 hours.After a prescribed period, the patient returns the data recorder to theclinician who then uploads the data onto a computer for subsequentviewing and analysis. The capsule is eliminated through the rectum andneed not be recovered.

The capsule camera of the prior art allows the GI tract from theesophagus down to the end of the small intestine to be imaged in itsentirety, although it is not optimized to detect anomalies in thestomach. Color photographic images are captured so that anomalies to bedetected need only have small visually recognizable characteristics, nottopography. The procedure is substantially pain-free and requires noanesthesia. The risk associated with the capsule passing through thebody is minimal—certainly, the risk of perforation is much reducedrelative to traditional endoscopy. The cost of the procedure is lessthan for traditional endoscopy due to the decreased use of cliniciantime and clinic facilities, and without using anesthesia.

In the prior art, a wireless capsule camera stores a single data stream.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, a capsule cameraincludes a wireless transmitter that transmits data and a receivingsystem having multiple receiving units to allowing storing multiple datastreams simultaneously. The multiple stored data streams may be used ata later time to derive the best data stream for analysis, based on thenetwork conditions at the time each data packet is received.

In general, wireless transmission is error prone. Bit errors in codewordmay have a greater impact than the same number of bit errors in theimage data. For example, a bit error located in a codeword or a headerof a data packet is likely to be of greater consequence than a bit errorlocated in the encoded data portion representing an image pixel value.Therefore, it is possible that a receiver under better network conditionactually receives an encoded string that is more difficult to decodethan another receiver under an inferior network condition. Due to noisein the environment and multi-paths, sometime a signal with an error maybe received despite strong received signal strength. For the above andother reasons of secured wireless transmission, it is desirable to keepmultiple received data streams in the receiving units.

The best data stream may be derived from the multiple stored datastreams at a later time during the decoding process. For example, in acapsule camera application, the multiple data streams may be stored inthe memory devices associated with the receiving units, which aretypically attached to different locations on the body during diagnosis.The multiple data streams are maintained as the capsule passes throughthe gastrointestinal tract. Subsequently, after the diagnosis, thereceiving units are recovered and connected to a computer or anotherstandalone device for analysis. At that time, the best data stream isderived from the stored data streams using a decoding process, or bycomparing the decoded results.

To improve efficiency, not all receiving units store the data streams atthe same time. A screening process, for example, may be provided suchthat only the receiving units with better network conditions store thedata streams. In a real-time system, the data streams may be stored foronly a short duration before the best data stream is derived by adecoding process, or by comparing the decoded results.

The present invention is better understood upon consideration of thedetailed description below in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, according to one embodiment of the present invention,receiving units 03 (each including a wireless receiver) being attachedto human body 01.

FIG. 2A is a block diagram of exemplary receiving unit 03, in accordancewith one embodiment of the present invention.

FIG. 2B shows, in one exemplary implementation, antenna 11 being locatedon one side of receiving unit 03, while other components of receivingunit 03 are located on the other side.

FIG. 3 is a signal flow diagram of receiving unit 03, in accordance withone embodiment of the present invention.

FIG. 4A shows the protocol stacks in a capsule camera and a receivingunit, in accordance with one embodiment of the present invention, inaccordance with one embodiment of the present invention.

FIG. 4B shows passing network condition information to the top protocollayer of receiver 12 on separately provided path 22 without goingthrough the strict hierarchical layer convention.

FIG. 5A shows a process for selecting an optimal block N, during timeperiod T_(N), from the data streams recorded in the receiving units, inaccordance with one embodiment of the present invention.

FIG. 5B shows a selecting process in which the active time periods foreach receiver (labeled 03-1-T to 03-M-T, respectively) are provided asinputs to block selector 30, in accordance with one embodiment of thepresent invention.

FIG. 6 is a flow chart for selecting the Nth block in one implementationof block selector 30 of FIG. 5B.

FIG. 7A shows the connections and data flow between receiving units 03-1to 03-M and docket station 51 and between docket station 51 andworkstation 57.

FIG. 7B shows an alternative implementation in which hub or adaptor 56connects receiving unit 03-1 to 03-M to workstation 57.

FIG. 8 is a flowchart that illustrates activating and deactivating onereceiving unit 03, based on collected statistics that predict thelocation of a capsule camera.

FIG. 9 shows receiving units 03-1, 03-2 and other receiving units beingplaced on human body 01.

FIG. 10 shows an activation scheme for activating consecutively numberedreceiving units, according to one embodiment of the present invention.

FIG. 11A show a decoding process which provides a stream of blocks basedon network conditions and decoding criteria, in accordance with oneembodiment of the present invention.

FIG. 11B show a decoding process which provides a stream of blocks basedon network conditions and decoding criteria, in accordance with anotherembodiment of the present invention.

FIGS. 12A to 12E illustrate various placements of receiving units on apatient's body, in accordance with various embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A capsule camera that is equipped with a wireless transmitter isactivated for image data and other data transmissions as it travels in agastrointestinal tract. FIG. 1 shows, according to one embodiment of thepresent invention, receiving units 03 (each including a wirelessreceiver) being attached to human body 01. As shown in FIG. 1, receivingunits 03 are placed at various locations over intestine 02, which isunder examination, to receive image and other data from a capsule camerathat is traveling in the gastrointestinal tract. Although FIG. 1 showsseven receiving units, any suitable number of receiving units may beused. The number of receiving units is determined based on system designconsiderations, such as human body transmission and receiving errorrates. Each of receiving units 03 may be affixed to an assigned locationof the body by belt, band or tape.

FIG. 2A is a block diagram of an exemplary receiving unit 03, inaccordance to one embodiment of the present invention. As shown in FIG.2A, antenna 11 is provided for picking up a wireless signal. Thecaptured signal is provided to receiver 12 to recover the transmitteddata. The transmitted data includes both image data and other data. Suchother data includes, for example, the time at which each data block isreceived and the network condition at the time the data block isreceived. The received data is stored in archival memory 14, which maybe provided by a mini disk drive or a semiconductor memory device (e.g.,a non-volatile memory device). At a later time, the data in receivingunit 03 may be retrieved through workstation/docket system interface 15into an intermediate docketing system or directly into a workstation.Workstation/docket system interface 15 may be provided by a serialinterface (e.g., USB) or a parallel port (e.g. PCMCIA).Controller/processor 13 controls receiving unit 03's operations and mayhandle other suitable functions, if required. This signal flow isrepresented in the flow diagram of FIG. 3. Battery 10, which may beprovided by one or more battery cells, powers receiving unit 03.

FIG. 2B shows, in one exemplary implementation, antenna 11 being locatedon one side of receiving unit 03, while other components of receivingunit 03 are located on the other side. Preferably, the antenna side ofreceiving unit 03 is provided on the side facing the human body to avoidthe transmitted signal from being shielded by the other components ofreceiver unit 03.

FIG. 4A shows the protocol stacks in a capsule camera and a receivingunit, in accordance with one embodiment of the present invention. Asshown in FIG. 4A, five communication protocol layers 1-5 are provided inboth the capsule camera and the receiving unit, each protocol layer inthe capsule camera having a peer protocol layer in the receiving unit.Of course, other implementations are possible. The physical layerscommunicate over a wireless medium between transmission antenna 04 ofthe capsule camera and receiving antenna 11 of the receiving unit. Thewireless medium includes the human body and possibly an air gap. Theprotocol decoder resides in receiver 12 (FIG. 3). Network conditioninformation is passed from layer to layer (i.e., 21 d, 21 c, 21 b to 21a, in that order) to the top protocol layer of the receiver 12, andretrieved by controller/processor 13 to be stored in archival memory 14.Each of interfaces 21 a-21 d has access to network condition informationof all the layers beneath it. FIG. 4B shows passing network conditioninformation to the top protocol layer of receiver 12 on separatelyprovided path 22 without going through the strict hierarchical layerconvention. This is convenient, as error conditions in each layer cannotbe anticipated by the peer protocol layers in the capsule camera.

In one system, a capsule camera traveling through the GI tract istracked by a number (e.g., M) of receiving units, with each receivingunit being provided to record one data stream and one set of networkconditions. At each receiving unit, the data stream may have gaps due tounfavorable network conditions during certain time periods. For example,suppose the probability of successfully transmitting a K-bit block ofdata is S (naturally, S≦1.0). Under the same network condition, theprobability for successfully transmitting a 2K-bit block would be S².Thus, for a large enough K, the probability of error-free transmissionmay be impractically low. This consideration is particularly relevant,as the capsule camera is moving through the body during this time, sothat the capsule camera may pass through a section of the GI tract wherethe K-bit block is optimal into another section of the GI tract where aK-bit block may be too large and thus the associated transmission timeis too long. Because the network conditions along the GI tract may varyand the speeds at which the capsule camera moves in the GI tract mayalso vary along the GI tract, the value K of the optimal block size atany given time depends in general on both the locations of the capsulecamera in the GI tract and the associated receiving unit.

Some encoding algorithms must operate within a defined encoding/decodingdata unit (e.g., an image area between restart markers, a slice or agroup of frames). An error in one data unit is not propagated to thenext data unit. Thus, in one embodiment, the optimal block size dependsalso on locations of the boundaries between encoding/decoding dataunits.

If the receiving units are placed at multiple locations (e.g., thelocations shown in FIG. 1), each receiving unit must keep track of time,so that the individually stored received data blocks of these receivingunits may be correlated to allow assembling into a single data stream ata subsequent time for viewing or processing. The single data stream maybe derived in a dedicated system, a docket system, or a workstation. Theclock signals in the receiving units must be synchronized with respectto each other at the beginning of data collection to accuracy (expressedin ppm) within a predetermined value. That is, synchronization must takeplace at the start or not long before the start of data collection(e.g., at the time the receiving units are placed on the patient's body)by a docket system or by a workstation. In one embodiment,synchronization is performed by resetting all receiving unitssimultaneously or by synchronizing two or more receiving units at atime, until all receiving units are synchronized with respect to eachother. If the transmission time for a block is T_(S), then eachreceiving unit clock must be kept accurate to an error of less thanT_(S)/2 over the entire duration of diagnosis. Alternatively, timinginformation may be transmitted by the capsule camera along with theimage or other data to mark the time at which the image or other data iscollected. The frequency at which such timing information must betransmitted is such that, in general, the greatest time differencebetween any two receiving units is less than T_(S)/2. In this way, it isnot necessary to synchronize the time of receiving units at thebeginning and use a precision crystal oscillator to keep accurate time:an on-chip semiconductor clock circuit may be sufficient.

FIG. 5A shows a process for selecting, during time period T_(N), anoptimal block N from the data streams recorded in the receiving units,in accordance with one embodiment of the present invention. Such aselection process may be executed after diagnosis is complete, and afterthe receiving units are detached from the human body and are connectedto the docket system or workstation (e.g., such as a personal computer).A personal computer typically does not have sufficient input ports(e.g., USB ports) for connecting all the receiver units simultaneously.In that situation, a hub (e.g., a USB hub) may be used. The selectingprocess of FIG. 5A may be executed on the workstation. As shown in FIG.5A, to select the Nth block, block selector 30 selects one block from Mblocks (i.e., block 03-1-NI to block 03-M-NI), corresponding to the Mdata streams stored in the M receiving units 03-1 to 03-M, respectively.The selected block 33, is selected based on the network conditions03-1-NC to 03-M-NC, which are stored along with the image data in the Mreceiving units, respectively. There may be gaps in general in the datastream of each receiving unit. If no Nth data block—corresponding totime period T_(N)—is found in a particular receiving unit, blockselector 30 does not take into account an Nth block from that receivingunit.

If block selector 30 has determined that the best (N−1)th block camefrom a certain receiving unit data stream, then the receiving unit isalso favored in the Nth block selection (see reference numeral 31 inFIG. 5A). Weighting factor 32 may be provided to block selector 30, withthe weighting function being determined empirically. The process memorymay reach back to any number of blocks prior to the current Nth block,with each previous block being assigned a different weight, depending onthe time difference between the previous block and the current Nthblock.

As described below, during the course of diagnosis, a receiving unit maybe placed in a power-saving mode (e.g., turned off or put into a sleepmode). These inactive time periods may be predetermined time points orbe determined based on the progress of the diagnosis process and may berecorded in the receiving units as either active time periods orinactive time periods. FIG. 5B shows a selecting process in which theactive time periods for each receiver (labeled 03-1-T to 03-M-T,respectively) are provided as inputs to block selector 30. Blockselector 30 does not take into account any block transmitted during aperiod of time that is specified as an inactive time period for areceiving unit.

FIG. 6 is a flow chart for selecting the Nth block in one implementationof block selector 30 of FIG. 5B. As shown in FIG. 6, step 41 initializesto ‘1’ a current value for the running index of the receiving units.Step 42 initializes the selected block N to the label “no data,”indicating that the candidate blocks have not been selected. When it isdetermined that the current receiving unit is active (step 43), selector30 determines if data has been received into the application protocollayer (step 44). If the receiving unit is marked inactive, or if no datahas been received into the application protocol layer, the currentreceiving unit is skipped. Initially, the first receiver that is activefor the Nth block and which has received data into the applicationprotocol layer is designated the “champion” with its associated networkconditions (step 47) and selected as the selected Nth block (step 48).Thereafter, the network conditions of receiving units with active Nthblocks are compared one by one with the network condition of thechampion (step 46). If the network condition of a given block comparesfavorable over the network condition of the champion, the given block ismade the champion (step 47). Otherwise, the network condition of thenext receiving unit is examined. The champion existing after the blocksof all the receiving units have been examined is the selected Nth block.

The network condition in the physical layer may be a combination ofmeasured signal parameters (e.g., the peak-to-peak amplitude of thereceived signal, the frequency-phase lock condition, and the receivedsignal strength indicator (RSSI) output of the received signal). Forhigher protocol layers, the error check and correction statistics may beused to indicate network condition. For example, error statistics thatcan be used include, for example, the type of errors, where the errorsoccur and the portion of errors that are correctable. Another indicatoris the number of characters expected between data unit delimiters. Forany given block (e.g., the Nth block), there are many ways for comparingnetwork conditions between two receiving units.

After the capsule camera has traveled through the intended GI tract 02(i.e., after diagnosis is complete), receiving units, 03-1 to 03-M, arerecovered from human body 01 and connected to docket system 51 orworkstation 57 for further processing. FIG. 7A shows the connections anddata flow between receiving units 03-1 to 03-M and docket station 51 andbetween docket station 51 and workstation 57, which may be a personalcomputer or another dedicated computational hardware. Docket system 51may be provided with physical connection sockets for the receiving units(not shown), controlled by receiving unit interface logic 54, andprocessor 53. In addition, docket system 51 includes work stationinterface 56 and working memories 55. Processor 53 may be dedicatedhardware, one or more processors, or a combination of processors anddedicated hardware. Docket system interface 56 connects to workstation57, where the processed image data and other data are stored, analyzed,further processed or are sent to display. In one implementation, theblock selecting processes described in conjunction with FIG. 5A or 5Bmay be implemented in docket system 51 or workstation 57.

FIG. 7B shows an alternative implementation in which hub or adaptor 56connects receiving unit 03-1 to 03-M to workstation 57. In thisimplementation, one of the block selecting functions described above inconjunction with FIGS. 5A and 5B or FIG. 11A or 11B is implemented inthe workstation 57. In FIGS. 7A and 7B, data flows from the receivingunits (i.e., receiving units 03-1 to 03-M) to docket system 51 and toworkstation 57, control signals may be bi-directional. In oneimplementation, power may be supplied to receiving units 03-1 to 03-M bydocket system 51 or workstation 57. In one implementation, power todocket system 51 is supplied by workstation 57.

While FIG. 1 shows all receiving units (i.e., receiving units 03-1 to03-M) to be active during diagnosis, the capsule camera in the GI tracts02 is at a single location at any given time. By measuring asufficiently large number of patients under similar medical conditions,it is possible to collect statistics on the required time for thecapsule camera to reach any of a number of locations of interest in theGI tract. Using such statistics, at the time the capsule camera isexpected to arrive at an area of interest, over or near which areceiving unit is positioned, the specific receiving unit may beactivated, while the other receiving units may remain in an inactivemode. Alternatively, the specific receiving unit and its immediateneighbors may be activated. In one embodiment, a receiving unit may beplaced to serve two areas of interest, based on the statistics ofexpected capsule passing times at the two locations.

FIG. 8 is a flowchart that illustrates activating and deactivating onereceiving unit 03, based on collected statistics that predict thelocation of a capsule camera. After synchronizing all clock signals(step 60), the receiving unit goes into an inactive mode (61) and isactivated when the current time reaches a start time at which thecapsule camera is expected to arrive at the location of the receivingunit (steps 62-64). During the period the capsule camera is active,image and other data are collected and transmitted. The capsule camerareturns to the inactive state when a stop time is reached (steps 65-67).The stop time is the expected time at which the capsule camera passesout of the area of interest relevant to the receiving unit. To ensurethat image data of the area of interest is properly captured, nearbyreceiving units may be activated, even when these nearby receiving unitsare placed outside of the zone within which the capsule camera is likelyto be.

FIG. 9 shows receiving units 03-1, 03-2 and other receiving units beingplaced on human body 01. Receiving units 03-1, 03-2 and others may beconnected by bus 04, for example. Bus 04 may be used to carry data,control signals, timing information, clock signals and power supply. Thereceiving units of FIG. 9 may be connected by wired or wireless links.In one embodiment, receiving units 03 may communicate with each other orat least with neighboring receiving units.

FIG. 10 shows an activation scheme for activating consecutively numberedreceiving units, according to one embodiment of the present invention.As shown in FIG. 10, receiving units 03 are consecutively numbered from03-1 to 03-M and placed in numerical order along GI tract 02 in themouth to anus direction. For example, to examine the entire colon,receiving unit 03-1 may be placed over the colon closest to ileocecalvalve. Once the capsule camera (not shown) arrives at the smallintestine-colon interface (i.e., the ileocecal valve), first receivingunit 03-1 is readily activated and ready for receiving data transmittedfrom the capsule camera. In FIG. 10, to ensure signal capture, receivingunit 03-2 is also activated (steps 70-71). Under the activation schemeof FIG. 10, the network conditions at the activated receiving units areused to select which one of the activated receiving units is the currentreceiving unit. When the network condition S2 detected at receiving unit03-2 is more favorable than the network condition S1 detected atreceiver 03-1, the current receiving unit is set to receiving unit 03-2,and receiving unit 03-3 is activated (steps 72, 80-83). As the capsulecamera moves to a position next to receiving unit 03-NM, the activationscheme makes receiving unit 03-NM the current receiving unit, whilehaving, at the same time, receiving units 03-(NM−1) and 03-(NM+1)activated (steps 72-78). Receiving unit 03-(NM−2) is deactivated whenreceiving unit 03-(NM+1) is activated (step 78).

From time to time, the capsule camera may retrograde, so that thenetwork condition S(NM−1) at receiving unit 03-(NM−1) may actuallybecome more favorable than network condition 03-(NM) at receiving unit03-(NM). When that situation arises, the current receiving unit is resetto 03-(NM−1) (steps 72-75, 84-85). In the activation scheme of FIG. 10,the activated receiving units are the current unit and one receivingunit in each of the forward and backward directions. In general, it isnot necessary to have equal number of activated receiving units in theforward and backward directions. For example, we may have d+ receivingunits in the forward direction and d− receiving units in the backwarddirection. For NM=5, with d+=2 and d−=1, the activated receiving unitsare receiving units 03-5, 03-6, 03-7 and 03-4. Furthermore, at differentsections of the GI tract, as motility may be different, having differentd+ and d− values may be appropriate. In one embodiment, when comparingnetwork conditions (e.g., at decision points 75, 81, 84 and 90), thecurrent receiving unit may be assigned a more favorable weightingfactor. Steps 89-92 handle the last receiving unit 03-M, when receivingunits 03-M and 03-(M−1) are activated.

The activation schemes provided in FIG. 8 (i.e., according to expectedtransit times) and FIG. 10 (i.e., according to received signalstrengths) may simplify the calculations required in the block selectingprocesses illustrated in FIGS. 5A and 5B. These activation schemes mayalso simplify the decoding selecting process of FIGS. 11A and 11Bdiscussed below. The activation schemes may also save power and storagearea, may reduce the reception and storage of erroneous data, and mayreduce the electromagnetic interference (EMI) of the total systemoperation. In the block selecting processes of FIGS. 5A and 5B, oneblock is selected based on network condition. However, different biterrors have different impact on the affected block or data stream. A biterror in a codeword may cause, for example, the codeword to become acodeword with a different run length. Such an error has a greater impactduring decoding than a bit error in a pixel value. Although an errorresilient coding/decoding may be applied, such a procedure incurs apenalty on the compression ratio, complexity and power, which are allcritical considerations in capsule camera design (in fact, on allhandheld wireless devices, in general). Even with an error resilientcoding/decoding, error-free operation is not guaranteed. So the decodingprocess itself is the best selection mechanism, if the block selectionprocesses of FIGS. 5A and 5B may result one or more best candidates foreach block.

FIG. 11A show a decoding process which provides a stream of blocks basedon network conditions and decoding criteria, in accordance with oneembodiment of the present invention. In FIG. 11A, consecutive blocksequences N to N+4 include a decoding interval (i.e., a data unit fordecoding). In this embodiment, the best stream of blocks are selectedfrom blocks received into different receiving units (i.e., receivingunits LL, MM, NN and OO) at different block sequences according tonetwork conditions. At block sequence N, for example, block 100—which isreceived into receiving unit MM—is selected because it is associatedwith the strongest network condition. (It is preferred that the decodinginterval coincides with block boundaries, but the teachings of FIGS. 11Aand 11B are applicable to more general conditions). At block sequenceN+1, the decoding process of FIG. 11A selects block 101, which isassociated with the strongest network condition detected at receivingunit OO. At block sequence N+2, the block selector provides blocks fromonly two receiving units. Thus, the decoding process selects block 102,which is associated with the better network condition between receivingunits NN and OO. At block sequence N+3, the decoding process encountersa decoding error while decoding block 103, which is associated with thestrongest network condition among receiving units LL, MM, NN and OO.Therefore, the decoding process selects block 104, which is associatedwith the next best network condition (i.e., at receiving unit MM).Decoding restarts from where block 102 left off, so that the decodingprocess concatenates the decoded bits from blocks 102 and 104. Thedecoding process then selects block 105, which is associated with thestrongest network condition at block sequence N+4. The best data streamis therefore the decoded bits resulting from decoding the concatenatedbits within decoding interval from block 101, block 102, block 104, andblock 105.

FIG. 11B show a decoding process which provides a stream of blocks basedon network conditions and decoding criteria, in accordance with anotherembodiment of the present invention. In FIG. 11B, as in FIG. 11A,consecutive block sequences N to N+4 include a decoding interval. Inaddition, in FIG. 11B, Sk, Sk+1, Sk+2, Sk+3, and Sk+4 denote thestrongest network condition for block sequence N, N+1, N+2, N+3, N+4,respectively. As shown in FIG. 11B, as the decoding process proceedsfrom block sequence N to block sequence N+4, blocks 106, 107, 108, 110and 111 are selected according to the network condition at each blocksequence. However, while processing block 111, it is found that thetotal number of characters in the decoding interval do not match theexpected number of characters in the decoding interval. To correct thiserror, since block 108 is associated with the weakest network conditionamong the network conditions associated with blocks 106, 107, 108, 110and 111, the decoding process of FIG. 11B discards block 108, andselects instead block 109. Decoding completes using blocks 106, 107,109, 110 and 111. In general, the decoding error may be detected at anearlier time than at the end of the decoding interval (i.e., in block111). For those skilled in the art, suitable corrections during thedecoding process would be apparent from the examples provided in FIGS.11A and 11B, and their variations and modifications.

Although FIGS. 11A and 11B provide illustrative examples for compressedbit streams, using the decoding process to select the best streams ofblocks is applicable to any encoded data streams. The errors indelimiters or with inconsistent character lengths are more serious thanother bit errors. Thus, the decoding process is effective in selectingthe best stream of blocks. In other embodiments, the decoding processneed not complete to allow effective block selection. For example, it isalready beneficial if the decoding process merely checks the bit streamheader information, syntax, character lengths and other errors but doesnot actual perform decoding during selection of the best stream ofblocks. In other embodiments, the decoding, partial decoding, and errordetection processes may be carried out in the block selector, such asthat shown in conjunction with FIGS. 5A and 5B.

Block selections using the decoding process, such as illustrated byFIGS. 11A and 11B, may be implemented in docket system 51, workstation57 or both, to allow sharing of the computation load. If docket system51 and workstation 57 share the computation load, the data flow betweendocket system 51 and workstation 57 in FIG. 7A may be bi-directional forthe intermediate data. In one embodiment, the processing power in thereceiving units of FIGS. 7A and 7B may also be used as coprocessors.Thus, receiving units 03-1 to 03-M, docket system 51 and workstation 57may form a distributed computing system.

To reduce the processing time required to derive the best data streamout of multiple data streams, the selection process, such as illustratedby the processes discussed in conjunction with FIGS. 11A and 11B, may becarried out in the receiving units. While the receiving units arestoring received incoming streams, the processor in each receiving unitmay perform the tasks discussed in conjunction with FIGS. 5 a, 5 b, 11Aand 11B. In one embodiment, such processing may be carried out duringtimes when the processor can spare processing power and when thereceiving unit is supposed to be inactive, i.e. not receiving signals.In another embodiment, multiple processor units are provided incontroller/processor modules of FIGS. 2 and 3. In one embodiment, theprocesses are carried out according to a schedule that is based on thepower reserve on the battery of the receiving units, the elapsed timesince the capsule has been activated, and the received data.

As the capsule camera travels through the GI tract by peristalsis, thecapsule camera may not orient along a longitudinal direction of the GItract. Furthermore, the patient's GI tract has different shapes alongits length, at different locations and positions, which vary with thesubject's motion or body pose. Both the required antenna orientation andthe body tissue through which the wireless signal has to penetrate toreach the receiving unit are also constantly changing. The multi-pathsignals reflected through different tissues and bones will also bechanging. Therefore, FIGS. 12A-D show some receiving unit placementsthat achieve better overall error rate performance. FIG. 12E is anexample in which the antenna design is efficient or its power may beincreased, so that the antenna placement is less restricted.Consequently, the antenna may be placed where it provides greatercomfort to the patient and easier installation. In this embodiment, tape200 fixes receiving unit 03 in place.

The detailed description above is provided to illustrate specificembodiments of the present invention and is not intended to be limiting.Numerous variations and modifications within the scope of the presentinvention are possible. The present invention is set forth in thefollowing claims.

We claim:
 1. A receiver system for receiving image data from a capsule camera, comprising: a plurality of receiving units each comprising: an antenna for receiving a signal transmitted wirelessly from the capsule camera; a receiver circuit coupled to the antenna that (a) processes the signal received in the antenna to recover data encoded therein; (b) generates information indicative of a parameter of the received signal and (c) outputs a digital signal comprising digital data encoding the recovered data and the parameter of the received signal; and an interface receiving the digital data from the receiver circuit for connecting to a processing circuit that recovers the image data from the digital data, wherein the receiving unit operates in an active mode and an inactive mode, the receiving unit being put into the active mode according to a network signal condition detected at a second receiving unit in the active mode within a predetermined distance of the receiving unit, and the parameter of the received signal being indicative of the network signal condition at the time the signal is received into the receiving unit; and wherein the processing circuit couples to the interfaces of the receiving units to receive from each coupled interface the digital data output from the receiver circuit associated with the coupled interface.
 2. A receiver system as in claim 1, further comprises an archival memory for storing the digital data received into each receiving unit.
 3. A receiver system as in claim 1, wherein each receiver circuit comprising a processor unit for controlling the operation of the receiving unit.
 4. A receiver system as in claim 1, wherein the recovered data comprises image data.
 5. A receiver system as in claim 1, wherein the digital data output from the receiver circuits are each divided into blocks substantially synchronized in time across the receiving units, the processing circuit selects a block from the substantially synchronized blocks of the receiving units.
 6. A receiver system as in claim 5, wherein each receiving unit records a timestamp in the blocks it generates.
 7. A receiver system as in claim 5, wherein the capsule camera transmits a timestamp at predetermined intervals.
 8. A receiver system as in claim 5, wherein the substantially synchronized blocks are synchronized to within one half a duration of the substantially synchronized blocks.
 9. A receiver system as in claim 5, wherein the block is selected according weightings assigned to the receiving units.
 10. A receiver system as in claim 5, wherein the processing circuit selects the block according to the network signal conditions of the substantially synchronized blocks.
 11. A receiver system as in claim 10, wherein the digital data is further divided into decoding intervals, each decoding interval spanning one or more of the synchronized blocks.
 12. A receiver system as in claim 11 wherein, during a given decoding interval, the processing circuit selects a plurality of blocks, each selected block being selected from the substantially synchronized blocks within the given decoding interval.
 13. A receiver system as in claim 12, wherein the selected blocks are contiguous in time spanning the decoding interval.
 14. A receiver system as in claim 13, wherein the processing circuit perform decoding of the digital signal to select the image data.
 15. A receiver system as in claim 14 wherein, when the processing circuit encounters a decoding error in a selected block, the processing circuit substitutes the selected block by another block in the substantially synchronized blocks from which the selected block was first selected.
 16. A receiver system as in claim 11 wherein, when the processor circuit discovers that a bit length of the digital data in the decoding interval is other than an expected value, the processing circuit substitutes one of the selected blocks, the substituted selected block being the block corresponding to the block in the selected blocks having the least favorable network signal condition among the network conditions associated with the selected blocks.
 17. A receiver system as in claim 1, wherein the block selection takes into consideration only blocks transmitted from receiving units operating in the active mode.
 18. A receiver system as in claim 17, wherein the receiving units are put into active mode also according to an expected arrival time model for the capsule camera to travel in a human gastrointestinal tract.
 19. A receiver system as in claim 17, wherein the parameter of the received signal further comprises a value representative of the time at which the signal is received into the receiving unit.
 20. A receiver system as in claim 1, wherein the predetermined distance is a function of whether the receiving unit is located in a forward direction or located in a backward direction relative to the second receiving unit.
 21. A receiver system as in claim 1 wherein the inactive mode comprises a power-saving mode.
 22. A method for receiving image data from a capsule camera, comprising: providing a plurality of receiving units each comprising: an antenna for receiving a signal transmitted wirelessly from the capsule camera; a receiver circuit coupled to the antenna that (a) processes the signal received in the antenna to recover data encoded therein; (b) generates information indicative of a parameter of the received signal and (c) outputs a digital signal comprising digital data encoding the recovered data and the parameter of the received signal; and an interface receiving the digital data from the receiver circuit for coupling a processing circuit that recovers the image data from the digital data, wherein the receiving unit operates in an active mode and an inactive mode, the receiving unit being put into the active mode according to a network signal condition detected at a second receiving unit in the active mode within a predetermined distance of the receiving unit, and the parameter of the received signal being indicative of the network signal condition at the time the signal is received into the receiving unit; coupling the processing circuit to the interfaces of the receiving units; and from each coupled interface, receiving into the processing circuit the digital data output from the receiver circuit associated with the coupled interface.
 23. A method as in claim 22, wherein the receiving unit further comprises an archival memory for storing the digital data received into each receiving unit.
 24. A method as in claim 22, wherein each receiver circuit further comprises a processor unit for controlling the operation of the receiving unit.
 25. A method as in claim 22, wherein the recovered data comprises image data.
 26. A method as in claim 22, wherein the digital data output from the receiver circuits are each divided into blocks substantially synchronized in time across the receiving units, the processing circuit selects a block from the substantially synchronized blocks of the receiving units.
 27. A method as in claim 26, wherein each receiving unit records a timestamp in the blocks it generates.
 28. A method as in claim 26, wherein the capsule camera transmits a timestamp at predetermined intervals.
 29. A method as in claim 26, wherein the substantially synchronized blocks are synchronized to within one half a duration of the substantially synchronized blocks.
 30. A method as in claim 26, wherein the block is selected according weightings assigned to the receiving units.
 31. A method as in claim 26, wherein the block selection takes into consideration only blocks transmitted from receiving units operating in the active mode.
 32. A method as in claim 31, further comprising putting one of the receiving units into active mode according to an expected arrival time model for the capsule camera to travel in a human gastrointestinal tract.
 33. A method as in claim 31, wherein the parameter of the received signal further comprises a value representative of the time at which the signal is received into the receiving unit.
 34. A method as in claim 26, wherein the block selection circuit selects the block according to the network signal conditions of the substantially synchronized blocks.
 35. A method as in claim 34, wherein the digital data is further divided into decoding intervals, each decoding interval spanning a plurality of the substantially synchronized blocks.
 36. A method as in claim 35 wherein, during a given decoding interval, the block selection circuit selects a plurality of blocks, each selected block being selected from the substantially synchronized blocks within the given decoding interval.
 37. A method as in claim 36, wherein the selected blocks are contiguous in time spanning the decoding interval.
 38. A method as in claim 36, wherein the processing circuit performs decoding of the digital signal to select the image data.
 39. A method as in claim 38 wherein, when the processing circuit encounters a decoding error in a selected block, the processing circuit substitutes the selected block by another block in the substantially synchronized blocks from which the selected block was first selected.
 40. A method as in claim 38 wherein, when the processor circuit discover that a bit length of the digital data in the decoding interval is other than an expected value, the processing circuit substitutes one of the selected blocks, the substituted selected block being the block corresponding to the block in the selected blocks having the least favorable network signal condition among the network conditions associated with the selected blocks.
 41. A method as in claim 22, wherein the predetermined distance is a function of whether the receiving unit is located in a forward direction or located in a backward direction relative to the second receiving unit.
 42. A method as in claim 22, wherein the inactive mode comprises a power-saving mode. 